Despite making promises to release his tax records, Trump has balked at doing so, saying he won’t disclose the filings until the IRS finishes auditing his returns.

“We’re putting these out today to put pressure on Trump and the other candidates to release theirs,” said Rubio campaign spokesman Alex Conant.

Cruz, meanwhile, speculated that there could be “a number of bombshells” in Trump’s tax returns, from exaggerations about the celebrity businessman’s earnings to “significant contributions to Planned Parenthood.”

The two candidates now pressing Trump have not released their complete tax returns, as Mitt Romney did in 2012 and Hillary Clinton did last year. Both Rubio and Cruz produced the first two pages of their filings to the Internal Revenue Service, which don’t include key details about subjects such as their tax deductions.

Both Cruz and Rubio have left the door open to releasing more information, with Cruz essentially daring his opponents to go first.

“If Marco wants to release the complete thing for the recent years, I’m happy to do so as well,” Cruz said. But he reserved his sharpest comments for Trump, calling the front-runner’s delay “unprecedented in presidential politics.”

Every major party candidate since 1976 has released his full tax returns at some point during the campaign, according to Joseph Thorndike, a tax historian and contributing editor to Tax Notes, an accounting trade publication.

But while Thorndike faulted Trump for backing away from releasing his tax returns, he called partial releases such as those by Rubio and Cruz “fake transparency.”

“If you’re going to release your tax return, you need to release your tax return,” he said, calling such disclosure a rite of passage for candidates.

The tax returns released by the two lawmakers, combined with their previously released personal financial disclosures, offer an overview of their financial lives since arriving in the Senate.

Rubio released portions of his 2010 through 2014 returns on Saturday, adding to 10 years of tax documents he had previously made public.

Since winning election to office in Washington, they show Rubio’s income has ranged from $276,059 to $938,963, and he has paid between $46,500 and $254,894 in federal income tax. Most of the income came from a business that collected royalties on two books: Rubio’s memoir, “An American Son,” and a pre-campaign tract, “American Dreams.”

In 2012, Rubio’s most lucrative year, his effective tax rate topped out at a little more than 31 per cent. But by 2014, the family’s income dropped to $335,963, an amount on which the Rubio and his wife Jeanette paid a 24 per cent tax rate. Rubio’s earnings that year were padded by cashing out $68,241 from his retirement savings.

Cruz released portions of his 2011 through 2014 returns. They show he and his wife Heidi brought in an annual average of $1,131,792, with large portions of their income coming from Cruz’s work in 2011 and 2012 at the law firm Morgan, Lewis and Bockius, and his wife’s work at Goldman Sachs. Cruz also reported $190,000 in income coming from a book advance from Harper Collins in 2014.

The returns show that Cruz and his wife reported more than $5.2 million in income in those years and paid an average effective tax rate of 37.6 per cent.

The summary returns yield few details on either candidate’s charitable giving, but they indicate that the Texas senator, who has banked on the support of evangelicals and appealed to voters on matters of faith, hasn’t tithed a full 10 per cent of his income.

“All of us are on a faith journey, and I will readily admit that I have not been as faithful in this aspect of my walk as I should have been,” Cruz told the Christian Broadcasting Network in January.